The present invention generally relates to appliances used in orthodontics and more specifically to orthodontic archwires used to provide forces to correct malocclusions between the teeth in the dental arch.
An orthodontic archwire is provided to apply corrective clinical forces to a patient's dental arch. The orthodontic archwire with a single or multi curved plane fits into orthodontic appliances such as brackets which are applied to the patient's teeth. The archwire material will generally be supplied in a round, square, or rectangular cross-section. A preformed archwire shape is selected for use based on the optimal dental arch shape for the patient being treated. When the preformed archwire is engaged in a patient with malocclusions in the dental arch, forces are applied to the orthodontic appliances to align and level the patient's teeth into the planned dental arch.
FIGS. 1A and 1B depict, in plan and perspective views, respectively, a preformed archwire shape 10 and the three sections of the archwire with incremental increases in force 4 within the three distinct areas—anterior teeth 1 (the centrals, laterals, and cuspids; i.e., the teeth in the front of the dental arch), bicuspids 2 (the first and second bicuspids; i.e., the teeth between the cuspids and molars), and posterior teeth 3 (the molars; i.e., the teeth in the back of the dental arch). FIGS. 1C, 1D and 1E show three typical archwire cross-sections, i.e., respectively, round 6, square 7 and rectangular 8 cross-sections.
In orthodontics, various appliances are used to correct malocclusions of the teeth. During the treatment cycle, it is quite often necessary to impart forces on the teeth to move the teeth into their desired location. This movement of the teeth is generally treated through a combination of appliances with one of the most important being the orthodontic archwire. The orthodontic archwire is secured within brackets which are mounted onto a patient's teeth. Prior art orthodontic archwires have been limited in respect to their ability to provide optimal clinical forces and corrective measures to all areas within the dental arch simultaneously. The result is many sequencing of wires to engage certain teeth and not others or concerns that the necessary forces required for larger teeth may impact the health of the smaller ones.
U.S. Pat. No. 5,044,947 to Sachdeva et al. is an attempt to provide an orthodontic appliance made of a shape memory alloy comprising of a nickel, titanium, and copper composition which is formulated to provide the desired loading and unloading forces to the bracket.
U.S. Pat. No. 5,683,245 to Sachdeva et al. discloses an archwire made of a shape memory alloy having a preset shape for exerting forces on teeth during orthodontic treatment. The alloy, which preferably is comprised of at least three elements (e.g., Ni, Ti and Cu), has a transformation temperature (Af) greater than about 25° C., whereby the orthodontic archwire produces forces at normal mouth temperature which are greater than the forces produced at normal room temperature. The orthodontic archwire also preferably has a variable modulus of elasticity.
U.S. Pat. No. 5,259,760 to Orikasa also discloses an orthodontic arch wire capable of exerting forces on the dental arch that gradually vary in magnitude along the wire.